Rosenthal Collins Group, which previously employed Mahlmann in its Quantum Financial unit that was purchased by ING, filed suit in Cook County Circuit Court seeking damages in excess of $1 million.

Prime International Trading Ltd. claims damages of more than $3 million in another suit, charging ING and Mahlmann diverted customers of Prime in violation of an agreement under which ING cleared Prime trades.

A similar suit filed earlier this year by Chicago Corp. has been shifted to an arbritration hearing at the CBOT.